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Simplified dds to store only 1/4 of a sin wave in storage. works now.

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T-moe
2016-06-03 14:04:43 +02:00
parent f31bc7a855
commit 17fa0fb90f
1 changed files with 11 additions and 12 deletions
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23
dds.vhd
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@@ -40,14 +40,14 @@ architecture Behavioral of dds is
signal idx_phase : unsigned(phase_res-1 downto 0) := (others => '0'); signal idx_phase : unsigned(phase_res-1 downto 0) := (others => '0');
signal amp_rect, amp_saw, amp_tria, amp_sin : unsigned (adc_res-1 downto 0); signal amp_rect, amp_saw, amp_tria, amp_sin : unsigned (adc_res-1 downto 0);
--type storage is array (((2**phase_res)/4)-1 downto 0) of unsigned (adc_res-2 downto 0); type storage is array (((2**phase_res)/4)-1 downto 0) of unsigned (adc_res-2 downto 0);
type storage is array (((2**phase_res))-1 downto 0) of unsigned (adc_res-1 downto 0); --type storage is array (((2**phase_res))-1 downto 0) of unsigned (adc_res-1 downto 0);
function gen_sin_wave return storage is function gen_sin_wave return storage is
variable temp : storage; variable temp : storage;
begin begin
forLoop: for i in 0 to temp'high loop forLoop: for i in 0 to temp'high loop
--temp(i) := to_unsigned(integer(real((2**(adc_res-1))-1)*sin((real(i)*MATH_PI/2.0)/real(temp'high))),adc_res-1); temp(i) := to_unsigned(integer(real((2**(adc_res-1))-1)*sin((real(i)*MATH_PI/2.0)/real(temp'high))),adc_res-1);
temp(i) := to_unsigned(integer(real(2**(adc_res-1) -1) + real((2**(adc_res-1))-1)*sin((real(i)*MATH_PI*2.0)/real(temp'high))),adc_res); --temp(i) := to_unsigned(integer(real(2**(adc_res-1) -1) + real((2**(adc_res-1))-1)*sin((real(i)*MATH_PI*2.0)/real(temp'high))),adc_res);
end loop; end loop;
return temp; return temp;
@@ -76,20 +76,19 @@ begin
idx_phase <= idx(acc_res -1 downto acc_res - phase_res); idx_phase <= idx(acc_res -1 downto acc_res - phase_res);
amp_sin <= sin_wave(to_integer(idx_phase));
-- Modulo is only required to prevent a synthesizer warning, but the value is actually never > 2**phase_res/4 --amp_sin <= sin_wave(to_integer(idx_phase));
--amp_sin <= to_unsigned((2**(adc_res-1)) - 1,adc_res) + sin_wave(to_integer(idx_phase) mod ((2**phase_res)/4)) when idx_phase(phase_res-1 downto phase_res-2)="00" else amp_sin <= to_unsigned((2**(adc_res-1)) - 1,adc_res) + sin_wave(to_integer(idx_phase(phase_res-3 downto 0))) when idx_phase(phase_res-1 downto phase_res-2)="00" else
-- to_unsigned((2**(adc_res-1)) - 1,adc_res) + sin_wave(to_integer(((2**phase_res)/2)-idx_phase) mod ((2**phase_res)/4)) when idx_phase(phase_res-1 downto phase_res-2)="01" else to_unsigned((2**(adc_res-1)) - 1,adc_res) + sin_wave(to_integer(((2**(phase_res-2))-1) - idx_phase(phase_res-3 downto 0))) when idx_phase(phase_res-1 downto phase_res-2)="01" else
-- to_unsigned((2**(adc_res-1)) - 1,adc_res) - sin_wave(to_integer(idx_phase-((2**phase_res)/2)) mod ((2**phase_res)/4)) when idx_phase(phase_res-1 downto phase_res-2)="10" else to_unsigned((2**(adc_res-1)) - 1,adc_res) - sin_wave(to_integer(idx_phase(phase_res-3 downto 0))) when idx_phase(phase_res-1 downto phase_res-2)="10" else
-- to_unsigned((2**(adc_res-1)) - 1,adc_res) - sin_wave(to_integer(((2**phase_res)-1)-idx_phase) mod ((2**phase_res)/4)); to_unsigned((2**(adc_res-1)) - 1,adc_res) - sin_wave(to_integer(((2**(phase_res-2))-1) - idx_phase(phase_res-3 downto 0)));
with form select amp <= amp_rect when "00", with form select amp <= amp_rect when "00",
amp_saw when "01", amp_saw when "01",
amp_tria when "10", amp_tria when "10",
amp_sin when others; amp_sin when others;
P1: process(clk) P1: process(clk)
begin begin
if(rising_edge(clk)) then if(rising_edge(clk)) then